HEADLIGHT &AMP; TURN SIGNAL ASSEMBLY

Toyota Corolla

Our teenage son had an accident tonight in which he shattered the headlight and turn signal assemblies on his 1991 Toyota Corolla (4dr Sedan). I believe that we need to get a turn signal and headlight assembly and install them. Is this pretty self explanatory once we get them or there anything we should know? Also there seems to be a long screw on the bottom side that seems to go back in very far and we cannot seem to get out. What is this for? It has part of the old assembly attached to it.
Thanks.